The present invention relates to high speed generators and, more particularly, to high speed generators that are used with gas turbine engines such as those used in aircraft, tanks, ships, terrestrial vehicles, or other applications.
A generator system for a gas turbine engine, such as that found in aircraft, ships, and some terrestrial vehicles, may include three separate brushless generators, namely, a permanent magnet generator (PMG), an exciter, and a main generator. The PMG includes permanent magnets on its rotor. When the PMG rotates, AC currents are induced in stator windings of the PMG. These AC currents are typically fed to a regulator or a generator control device, which in turn outputs a DC current. This DC current next is provided to stator windings of the exciter. As the rotor of the exciter rotates, three phases of AC current are typically induced in the rotor windings. Rectifier circuits that rotate with the rotor of the exciter rectify this three-phase AC current, and the resulting DC currents are provided to the rotor windings of the main generator. Finally, as the rotor of the main generator rotates, three phases of AC current are typically induced in its stator, and this three-phase AC output can then be provided to a load such as, for example, an aircraft, ship, or vehicle electrical system.
Because some aircraft generators are high speed generators with potential rotational speeds up to and in excess of 24,000 rpm, potentially large centrifugal forces may be imposed upon the rotors in generators. Given these potentially stressful operating conditions, the rotors should be carefully designed and manufactured, so that the rotors are reliable and precisely balanced. Improper balancing not only can result in inefficiencies in the operation of a generator, but may also affect the reliability of in the generator.
Among the components of a rotor that provide increased reliability and proper balancing of the rotors are the wire coils wound on the rotor. The centrifugal forces experienced by a rotor may be strong enough to cause bending of the wires of these coils into what is known as the interpole region. Over time, such bending can result in mechanical breakdown of the wires and compromise of the coil insulation system. Additionally, because the coils are assemblies of individual wires that can move to some extent with respect to one another and with respect to the remaining portions of the rotors, the coils are a potential source of imbalance within the rotor and can potentially compromise the insulation system. Even asymmetrical movements of these coils on the order of only a few thousandths of an inch can, in some instances, be significant.
In order to improve the strength and reliability of the wire coils and the coil insulation system, and to minimize the amount of imbalance in the rotors that may occur due to the wire coils, the rotors may include a coil retention system. With a coil retention system, substantially rigid wedges are inserted in between neighboring poles of the rotors to reduce the likelihood of coil wire bending or movement. In some embodiments, the wedges may also exert some force onto the coils to help maintain the physical arrangement of the coils.
In addition to the rotor, various other mechanical components within the generator rotate at high speeds and thus may be supplied with lubricant. Moreover, some of the electrical components within the generator may generate heat due to electrical losses, and may thus be supplied with a cooling medium. The lubricating and cooling media may be supplied from different systems, or from a single system that supplies a fluid, such as oil, that acts as both a lubricating and a cooling medium. The lubricating and cooling medium supplied to the generator may flow into and through the shaft on which the main generator rotor is mounted, and be supplied to the various mechanical and electrical components via flow orifices formed in the shaft.
Among the electrical components that may generate heat during generator operation are the rotor coils. In some generator designs, the wedges of the coil retention system are configured to allow a portion of the lubricating and cooling medium to flow through them. As the medium flows through the wedges it removes heat generated in the coils. In some generators, these wedges consist of multiple structural components that are joined together. As was noted above, these components may experience large centrifugal forces during rotor rotation, which may cause leaks where the structural components are joined. Because the wedges should be leak-tight, any leakage or failure of a wedge requires disassembly of the generator, and replacement of the wedge. This can be a time-consuming and expensive operation.
Although the wedges employed in conventional coil retention systems operate safely, the design of these conventional wedges also limits their effectiveness. Hence there is a need for a coil support wedge that can provide sufficient support for the rotor coils during generator operation and that can provide relatively leak-tight cooling for the coils and/or is less susceptible to leaks and/or reduces the likelihood of wedge replacement. The present invention addresses one or more of these needs.
The present invention provides a coil support wedge that is integrally formed and includes internal flow passageways that are substantially fluid tight, thereby increasing the overall reliability of the generator by making it less likely to undergo support wedge replacement or servicing.
In embodiment, and by way of example only, a high speed generator includes a stator and a rotor. The rotor is rotationally mounted within the stator and includes a shaft, at least first and second poles, and a coil support wedge. Each pole extends radially outwardly from the shaft and the poles are spaced apart from one another to form an interpole region therebetween. The coil support wedge is positioned in the interpole region and includes an integrally formed, longitudinally extending main body, and first, second, third, and fourth fluid passageways. The main body has at least a first end, a second end, and an outer surface. The first fluid passageway has an inlet port formed in the support wedge first end and an outlet port formed in the support wedge second end. The second fluid passageway has an inlet port formed in the support wedge second end and an outlet port formed in the support wedge first end, and its inlet port is in fluid communication with the first fluid passageway outlet port. The third fluid passageway has an inlet port formed in the support wedge first end and extends at least partially into the support wedge to an end. The fourth fluid passageway has an outlet port formed in the support wedge first end and extends at least partially into the support wedge to an end, the end of the fourth fluid passageway is in fluid communication with the end of the third fluid passageway.
In another exemplary embodiment, a rotor for use in a high speed generator includes a shaft, at least first and second poles, and a coil support wedge. Each pole extends radially outwardly from the shaft and the poles are spaced apart from one another to form an interpole region therebetween. The coil support wedge is positioned in the interpole region and includes an integrally formed, longitudinally extending main body, and first, second, third, and fourth fluid passageways. The main body has at least a first end, a second end, and an outer surface. The first fluid passageway has an inlet port formed in the support wedge first end and an outlet port formed in the support wedge second end. The second fluid passageway has an inlet port formed in the support wedge second end and an outlet port formed in the support wedge first end, and its inlet port is in fluid communication with the first fluid passageway outlet port. The third fluid passageway has an inlet port formed in the support wedge first end and extends at least partially into the support wedge to an end. The fourth fluid passageway has an outlet port formed in the support wedge first end and extends at least partially into the support wedge to an end, the end of the fourth fluid passageway is in fluid communication with the end of the third fluid passageway.
In yet a further embodiment, an interpole coil support wedge for placement in an interpole region that is formed between adjacent poles of a rotor assembly includes an integrally formed, longitudinally extending main body, and first, second, third, and fourth fluid passageways. The main body has at least a first end, a second end, and an outer surface. The first fluid passageway has an inlet port formed in the support wedge first end and an outlet port formed in the support wedge second end. The second fluid passageway has an inlet port formed in the support wedge second end and an outlet port formed in the support wedge first end, and its inlet port is in fluid communication with the first fluid passageway outlet port. The third fluid passageway has an inlet port formed in the support wedge first end and extends at least partially into the support wedge to an end. The fourth fluid passageway has an outlet port formed in the support wedge first end and extends at least partially into the support wedge to an end, the end of the fourth fluid passageway is in fluid communication with the end of the third fluid passageway.
Other independent features and advantages of the preferred coil support wedge will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.